1. Field of the Invention
The present invention relates to an automobile fuel container material and an automobile fuel container that are excellent in formability, weldability, corrosion resistance of a paint film, and corrosion resistance to gasoline and, at the same time, have improved (excellent) environmental adaptability, that is, are free from lead, which poses an environmental hygiene problem, and are free from the elution of chromium(VI).
2. Background Art
A terne plated steel sheet, which is a steel sheet plated with a lead-tin alloy having a tin content of 3 to 20% by weight, has hitherto been extensively used as an automobile fuel container material. This terne plated steel sheet is excellent in properties such as formability at the time of forming of the steel sheet into a fuel container, seam weldability, corrosion resistance of internal surface to a gasoline fuel, and corrosion resistance of external surface after painting. However, due to an increasing demand for global environmental protection in recent years, the terne plated steel sheet has become regarded as a problematic steel material. Specifically, there is an ever-increasing strong demand for the regulation of the elution of lead from industrial wastes such as shredder dust, and, since the terne plated steel plate, which is a steel plate plated with a lead-tin alloy, contains a large amount of lead, there is a tendency toward the restriction of the use of the terne plated steel sheet.
To cope with this, several steel plates with a lead-free plating have been developed and put to practical use as an alternative to the terne plated steel plate. For example, Japanese Patent Laid-Open No. 183368/1998 discloses a rust preventive steel sheet for a fuel tank wherein the surface of a steel sheet with a hot dip aluminum plating has been covered with a chromate film formed by coating, dipping, spraying or the like. This aluminum plated steel sheet, however, is expensive. Further, since a brittle iron-aluminum-silicon (Fe—Al—Si) alloy layer is formed at the interface of the steel sheet and the plating, the separation of the plating and cracking are likely to occur and the formability of this plated steel sheet is poor. In addition, harmful chromium(VI) is contained in the chromate film formed by coating, dipping, spraying or the like. Therefore, as with the case of lead, the aluminum plated steel sheet covered with the chromate film poses a problem that chromium(VI) is eluted from industrial wastes such as shredder dust.